Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $118.37   6.263%   $125.7835   $125.78   $125.80   $125.80  
  Purchase #2 $61.58   8.561%   $66.8519   $66.85   $66.85   $66.90  
  Purchase #3 $236.92   9.191%   $258.6953   $258.70   $258.70   $258.70  
  Purchase #4 $127.82   5.305%   $134.6009   $134.60   $134.60   $134.60  
  Purchase #5 $41.82   12.288%   $46.9588   $46.96   $46.95   $47.00  
  Purchase #6 $189.25   13.557%   $214.9066   $214.91   $214.90   $214.90  
  Purchase #7 $197.34   11.264%   $219.5684   $219.57   $219.55   $219.60  
  7 purchase totals = $973.10       $1,067.3654   $1,067.37   $1,067.35   $1,067.50